“Probably the best thing to do,” counseled the navigation section of the Boy Scout Handbook’s 1940 edition, “is not to get lost.”

Not everyone agrees. For some, the temptation to cast off the strictures of civilization by fleeing indefinitely into the woods, the desert or the mountains is intoxicating. “People have sought out solitary existences,” Michael Finkel writes in The Stranger in the Woods, “at all times across all cultures.” Hermits are mentioned in “Chinese texts etched on animal bones” and in the Epic of Gilgamesh, which dates back some 4,000 years. They are venerated by the major religious traditions. Like wild plants, they can be hard to tell apart at first glance but differ widely in their particulars: “The nineteenth century brought Thoreau; the twentieth, the Unabomber.”

The most perplexing living hermit is Christopher Knight, who took the road less traveled into a Maine forest and avoided human contact for nearly three decades. When Knight reappeared in 2013, the only way he could date his escape was by asking when the Chernobyl disaster occurred.

Rather than practice true self-reliance, like a “Foxfire” devotee or a Slab City off-gridder, Knight kept himself alive by stealing from unattended cabins in the vicinity of North Pond and Little North Pond, bordered by Mercer, Rome and Smithfield, Maine. Having long since achieved the mythical status of a Sasquatch or Jersey Devil among locals, Knight was caught by Terry Hughes, a game warden and a former U.S. Marine, while burglarizing the Pine Tree Camp in Rome. The story that emerged following his capture was so strange that the justice system scarcely knew what to do with him.

Knight had abandoned his car and entered the woods in 1986 at age 20, without any forethought or supplies. He found his way to a dense, barely navigable stretch known to locals as the Jarsey, where he established a camp hidden by boulders, trees and homemade camouflage. He proceeded to commit, over twenty-seven years, more than 1,000 burglaries—likely “the biggest burglary case in the history of Maine”—of food, alcohol, apparel, camping equipment, batteries, propane tanks, radios, tools, magazines and books. The magazines he read and then repurposed into “bricks” with which he built a rainwater-draining floor. The books were something more.

The Stranger in the Woods is a meditation on solitude, wildness and survival. It is also, unexpectedly, a tribute to the joys of reading. The time Knight didn’t spend daydreaming, thieving or courting death by exposure—he lived in a structure made of tarps and claimed he never lit a fire—he spent reading everything he could get his hands on. He favored the Tao Te Ching; Shakespeare; Robinson Crusoe (naturally); Edna St. Vincent Millay; and William Shirer’s The Rise and Fall of the Third Reich (amusingly, he admired its concision). He hated Thoreau and Frost. He read John Grisham, then used the pages as toilet paper. When there was nothing else around, he settled for Harlequin romances; he had never been on a date in his life.

Knight’s rejection of companionship other than books was total. He was afraid to have a pet, since he might have to compete with it for food or, worse, eat it. The closest he came to one was the shelf mushroom that he watched grow from the size of a “watch face” to that of a “dinner plate” over the decades, or the fireflies that appeared each year around Independence Day. He enjoyed music, particularly classic rock (“They will be playing Lynyrd Skynyrd songs in a thousand years,” he told the author), but not religion; he never stole a Bible and considered himself a mixture of Stoic and animist. The only time he prayed, he said, was for warmth. Nevertheless, he was ashamed on principle to be a thief. He didn’t want his aged mother—who so firmly believed in privacy and independence that she hadn’t even filed a missing-person report—to learn about his self-serving predations.

Awaiting his trial, Knight described jail as “Bedlam” and wished that he were in solitary confinement. The state of Maine found him competent to stand trial, but suggested various diagnoses: autism spectrum disorder, depression, and schizoid personality disorder. Maeghan Maloney, the prosecuting district attorney, noted that “the law is not set up for an outlier case like this.” And so, despite being one of the most prolific burglars in history, Knight pled guilty to a mere thirteen counts and was admitted into a program that “substitutes counseling and judicial monitoring” for prison time.

The people of Maine were divided on this outcome. Some found Knight colorful and felt he ought not to be judged too harshly. They wanted to contribute money to his defense—or to purchase land on which he could continue to squat. A popular deli sold a sandwich called the Hermit, made with “all locally stolen ingredients.” Other Mainers hated Knight for plundering that most precious commodity: their peace of mind. A great many insisted, to Knight’s consternation, that he was a liar, that he could not have survived all those Maine winters without help. Law enforcement officials disagree. Like Mr. Finkel, they see a singular, troubled individual who just wasn’t made for these times. The author, whose relationship with the prickly Knight never rises to the level of friendship, presents a figure who just, like Greta Garbo, wants to be alone.

Mr. Finkel sees Knight as a link in a long chain of men and women, religious and secular in motivation, who have sought total solitude: the ascetic Desert Fathers of early Christian monasticism; the ornamental hermits of eighteenth-century English estates; the Japanese hikikomori of today. Knight’s words upon returning to modern society say all that needs to be said: “It’s too loud. Too colorful. The lack of aesthetics. The crudeness. The inanities. The trivia. The inappropriate choices of aspirations and goals.” We have all, perhaps, felt this way at one time or another. What none of us has done is threaten to walk deep into the woods to die willingly of hypothermia. What none of us has done is vanish completely.

Mr. Finkel reached out to Knight because he was motivated by “some degree of respect and a great deal of astonishment.” Had Knight never been caught, Mr. Finkel writes, “It would have been an existence, a life, of utter perfection.” Given the absurdities and indignities of modern life, it is little wonder Knight’s choices look to Mr. Finkel perfectly sane.